1. Field of the Invention
The present invention relates to body implants. More particularly, the present invention relates to a radioactive filament comprising an iridium/platinum alloy core and a pure platinum sheath, which can be cut to predetermined lengths without unwanted leakage of the radioactivity, and a method of treating the implant for insertion into certain areas of the body for treatment of body tumors.
2. General Background
In the area of medicine that addresses the treatment of tumors in the body, one such method of treatment is the insertion of implants into the tumor which have been previously radioactive and that emit radioactivity in order to shrink or "kill" a tumor, referred to in the field as Interstitial Brachytherapy.
The procedure involved in this type of therapy would be to insert the radioactive implant through a plastic catheter that has been previously inserted into the tumor from the outside of the body. Once the implant is in the tumor, then the radioactivity emitted by the implant would hopefully destroy the cancerous cells around it. However, there are shortcomings to this technique in utilizing the particular type of implants presently on the market. One of the most common type of implants is the IR-192 seed implants which are iridium/platinum seeds spaced inside a nylon or plastic tube for insertion into the cancer. The IR-192 seeds are 3 mm in length and are commonly spaced 7 mm apart so that there exists a known standard distance of one (1) centimeter between the center of each seed. The IR-192 core contained in each of the seeds cannot be exposed at any of their surfaces to the exterior since the radioactivity would bleed from the iridium core and cause damage. Therefore, it is absolutely necessary that the iridium platinum core be in a sheath of platinum at all times. Since there is spacing between the seeds of the nylon or plastic tubing, when inserted into the body of a tumor, the portions of tubing which are not housing the iridium or IR-192 seeds are not emitting radioactivity, and thus the tumor is only being "partially" treated. Likewise, in the cases where the IR-192 seed must be inserted into an area of the body which is not straight, for example an endobronchial implant, tongue implants, tonsil implants, and many other areas that are not readily accessible for treatment, the catheter must be first put in place by traversing a difficult path composed of many turns, tight angles and curves in order to get to the area needing treatment. The IR-192 implant that is to be contained within the catheter can follow only after the tedious task of insertion of the catheters has been accomplished. Since there are spaces between the seeds, many times the nylon or plastic tubing will bend and kink as one attempts to make it move through the curvature of the catheter that leads to the area to be treated, and it becomes impossible to move any further.
Likewise, in addition to the IR-192 seeds, there are some products on the market that are being sold which are pre-determined lengths of encapsulated IR-192 wires. The IR-192 wire implant does have the significant advantage over the IR-192 seed due to the fact that it is a continuous treatment surface and does not contain gaps. However, its shortcomings is that it must be sold only in pre-determined lengths, since any attempt to cut the wire to more precise lengths would cause a leakage in the wire as it would not be self sealing and would thus be unacceptable for use.
Under present guidelines, a radioactive sealed source, whether it is in the form of a wire or seed, has to be leak tested at least every six months. Since the wire is sold in pre-determined lengths and is encapsulated, it is not leaking and is sold as such. Almost every body tumor to be treated is different in size and shape; and, in most cases, more than likely, the wire would have to be cut in order to precisely fit the tumor or cancer area. In the case of IR-192 wire, as was stated earlier, this cannot be done; and therefore, the tumor will not be properly covered.
Further, in order to get the implant (a radioactive part), into the upper lobe for an endobronchial implant, it is necessary that the IR-192 wire be placed into a 0.035" or 0.038" guidewire housing for maneuvering the implant around several curves, etc., within the body in order to reach the upper lobe. In this procedure, the implant is mounted inside a 0.035" or 0.038" guidewire and inserted through a special balloon catheter that is placed through the nasal passage and anchored into place inside the area needing treatment. The problem associated with passing the implant through the balloon catheter is that there is usually one or two sharp angles or curves along this route, especially when inserting into the upper lobe. Previously, in these areas where the curves are difficult, the pressure inserted in attempting to maneuver the implant through the curves would actually cause a kink where the implant and core inside the guidewire meet, allowing no further advancement of IR-192 wire implant. The area needing treatment could not always be reached. Therefore, there is a need to join the iridium wire to the stainless steel wire inside the guide-wire, so that no kinking will occur, and the implant can be inserted into the area that needs to be treated.
Further, in the area of brain implants, if the IR-192 wire implant would not join to a stainless steel wire of approximately the same outside diameter, the IR-192 wire would have to be mounted inside a small nylon catheter. For example, the nylon catheter presently used has an outer diameter of 0.85 mm. The wire alone is 0.4 mm. A brain implant procedure entails drilling a hole inside the brain for placement of the IR-192 wire. The catheter is slipped inside this hole. If the nylon catheter is used, a hole twice as large as what is needed inside the brain will have to be drilled. By joining the IR-192 wire to a stainless steel wire, one is able to lower it through a hole with the outside diameter smaller than 0.5 mm, since the diameter of the IR-192 wire is only 0.4 mm. Because of the high risk involved in drilling into the brain, the smaller hole is obviously a greater advantage.
U.S. patent application, Ser. No. 778,410, entitled "Iridium/Platinum Implant And Method Of Encapsulation", by the same inventor, now abandoned, disclosed the method by which an IR-192 platinum wire implant, having a core area comprised of 25% iridium and 75% platinum, could be cut to a proper length for use to treat tumors, whereby the method of cutting assured that the end portions of the implant were automatically sealed around the iridium/platinum core so that no radiative leakage would occur.
U.S. patent application, Ser. No. 897,544, entitled "Iridium/Platinum Implant, Method Of Encapsulation, And Method Of Implantation", also by the same inventor, claimed an improvement in the parent application, in that the method of preparing and implanting a radioactive implant into the body included a guide member that was secured to the implant for guiding the implant to the portion of the body, including a flexible housing for positioning the implant guide member within the housing. There was applied a compound to the exterior of the housing for achieving a bond between the exterior housing, the implant and guide member, so that the guide member and the implant could be maneuvered to an area of the body and kinking between the implant member and the guide member would be avoided.
There are several patents which were issued in the field, the most pertinent being as follows:
______________________________________ Patent No: Inventor: Invention: ______________________________________ 2,429,438 Wappler "Tubular Bodies Such As Radium Seeds" 2,322,902 Wappler "Apparatus For Making Tubular Bodies" 3,438,365 Packer, et al "Radioactive Seed Container Xenon Gas For Medical Treatment" ______________________________________